There is known a product sales data processing device. The product sales data processing device reads product information from an RFID (radio frequency identifier) tag which is attached to each product, and executes a sales registration and accounting process, based on the product information. For example, if products, or a shopping basket which contains products, is placed on an upper surface of a checkout counter in which a planar antenna is embedded, a reading device reads batchwise product information from the RFID tags attached to the products.
In addition, there is proposed a box-shaped reading device as another mode. In this reading device, a reading chamber for reading RFID tags is provided in a housing which is formed of a metal or the like. In addition, an opening-and-closing lid for accessing the reading chamber is provided in the housing. If products (shopping basket) are put in the reading chamber, the reading device reads batchwise the product information from the RFID tags attached to the products.
In the meantime, when reading is executed by using the above-described box-shaped reading device, the reading is started after the products are put in the reading chamber and the opening-and-closing lid is closed, in order to prevent a read error or the like. Then, after the reading is finished, the opening-and-closing lid is opened and the shopping basket is taken out from the reading chamber. However, for example, a user, who is unfamiliar with operations, may perform an improper operation. For example, the user may perform an improper operation, such as opening the opening-and-closing lid during reading, or forgetting to open the opening-and-closing lid after the end of reading. In such a case, there is a possibility that a delay occurs in processing. Thus, there is a demand for a technique which can provide a guidance on a proper operation method.